1. Field of the Invention
The present invention relates to liquid crystal display devices, and more particularly, to a device and a method for driving a liquid crystal display device in which the level of a gate driving voltage is varied in accordance with a swinging level of a common voltage to prevent distortion of an image signal being charged to each pixel region, thereby improving display quality of the image.
2. Discussion of the Related Art
With increased use of flat display devices, several flat panel technologies have emerged. There are liquid crystal display devices, field emission display devices, plasma display panel, light emitting display devices, and so on. Of the flat display devices, liquid crystal display devices, having excellent resolution, color expression and picture quality, are actively applied to notebook computers, desk top monitors, and mobile terminals.
Liquid crystal display devices display pictures by controlling light transmissivity of liquid crystals using an electric field. The liquid crystal display device is provided with a liquid crystal panel having a plurality of pixel cells for displaying the picture, a driving circuit for driving the liquid crystal panel, and a backlight unit for directing a light to the liquid crystal panel.
The liquid crystal panel controls transmissivity of the light from the backlight unit for displaying a desired picture with the plurality of pixel cells. The pixel cells receive an image signal from the data lines in response to a gate driving voltage received through the gate lines and vary an array of the liquid crystal molecules therein to control light transmissivity.
Consequently, in the related art, in order to increase the response speed of the liquid crystals and save power consumption of the liquid crystal panel, the level of the common voltage is made to swing in accordance with a polarity of the image signal before the common voltage is supplied to the liquid crystal panel. In particular, in order to increase the difference between the level of the image signal charged to each pixel cell and the level of the common voltage, the level of the common voltage is configured to swing such that a polarity and a magnitude of the image signal are opposite to that of the common voltage.
However, the related art common voltage swing causes distortion of image signals, resulting in poor display quality when the common voltage swing is applied to a large sized liquid crystal panel. In particular, because large sized liquid crystal panels are recently widely used, the related art common voltage swing is applied to the large sized liquid crystal panel, wherein an image signal charge time difference between an upper side and a lower side of the liquid crystal panel is large. Therefore, the display quality of the image becomes poor because of the difference of charge quantities of the image signal or the change of the voltage difference between the common voltage and the image signal.